The cut gene of the fruit fly encodes a putative transcription factor which is a key gene for specifying sensory organ identity. The long-term goals of my research are to understand the function and regulation of this gene as well as to search for new genes which interact with cut in sensory organ specification during neurogenesis. The specific aims are: (1)to determine the temporal and spatial requirements of cut in specifying the correct development of sensory organs, and to study the competence of cells in the embryo to respond to cut using inducible promoters in germline transformation experiments in vivo. (2)to identify regions of the regulatory domain of cut that contain promoter or enhancer elements responsible for the cut expression pattern in vivo (in conjunction with a reporter gene). (3)to search for genes that interact with cut. a) Mutagenesis and gene dosage experiments will be carried out to identify genes interacting genetically with cut. b) P-element insertion lines will be screened for insertions near genes that exhibit an cut dependent expression patterns suggesting a cut downstream function. c) In vitro DNA binding of the cut homeodomain to find elements in the genome near genes that are regulated by cut. Future interests are: to search for structurally homologous genes to cut in a quest for other neuronal regulatory genes with a similar function as cut. Vertebrate homologues of homeobox genes are preferentially expressed in the developing nervous system and neurological functions have ben attributed to them. The insights from studying neuronal regulatory genes in the fly will, therefore, contribute to an understanding of their counterparts in the mammalian brain.